A precision pointing system carrying a sensor, such as a telescope, as its payload may be susceptible to disturbances that produce structural vibrations and, consequently, pointing errors. Such vibrations may be attributed to mechanical components or assemblies, such as reaction wheel assemblies that are used as actuators in the precision pointing system. For the most part, because these systems tend not to have significant, inherent damping, these structural vibrations may degrade system performance and even cause structural fatigue over time.
To minimize structural vibrations, a system of vibration isolators is typically used to damp the structure and isolate the payload. A well-documented type of vibration isolator operates as a three-parameter vibration isolation system and includes a hollow shaft, a piston, and a main spring. The piston receives vibration from the payload and is configured to slidably move through the shaft in response to the vibration. A flange extends radially from a midsection of the piston and has a top surface that is coupled to a first sealed bellows and a bottom surface that is coupled to a second sealed bellows. Each of the bellows has a chamber that is filled with a fluid, such as a liquid. Thus, when the piston moves axially through the shaft, fluid flows from one of the bellows chambers to the other. The shaft and piston are disposed within the main spring, which provides axial stiffness to the vibration isolator in general. Although conventional vibration isolators, such as the one described above, are generally useful for damping vibrations in most circumstances, they may not operate as desired when employed in cryogenic (e.g., below about −120° C.) environments. In particular, the fluid that fills the chamber of the vibration isolator may change in viscosity and/or from a liquid state to a solid state when exposed to such temperatures.
Recently, magnetic isolation struts may have been used in cryogenic environments. Magnetic isolation struts include a shaft that receives vibration and a magnetic element adjacent the shaft that generates an electromagnetic force that can cause the shaft to resist motion to thereby dissipate the vibration. However, magnetic isolation struts may be relatively heavy, and may not be suitable for weight-limited applications. Moreover, magnetic isolation struts may not be as effective as desired in damping certain magnitudes of vibrations. Additionally, the magnetic element may produce a magnetic field, which may undesirably affect some payloads.
Accordingly, it is desirable to have a vibration damping system that may be used in a cryogenic environment while minimally affecting the operability of surrounding components, such as the payload. In addition, it is desirable to have a system that is relatively lightweight. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.